In such hollow shaft assemblies, the drive elements, such as the cams and driving pinions of a camshaft, are each produced as individual elements with through-apertures. The drive elements are then slid on to the hollow shaft or tube. Thereafter, a probe member is slid into the tube. The probe member comprises individual operating regions which are axially associated with the drive elements. Each operating region includes a probe portion which is delimited by two annular seals. A hydraulic medium can be applied in the operating region at a high pressure of up to 3000 bar, for example. As a result, the tube is plastically expanded in the respective longitudinal portion, thus securing the drive elements on the hollow shaft. The deformation of the drive elements preferably takes place in the purely elastic range.
U.S. Pat. No. 4,750,250 discloses, in general, a method and a device for simultaneously fixing a plurality of drive elements such as cams, gearwheels and bearing bushes on a hollow shaft in one operation. The problem of holding the drive elements in an accurate position relative to the hollow shaft, particularly with respect to angular accuracy, however, is not satisfactorily addressed.
U.S. Pat. No. 5,195,239 describes a method and a device for positioning all of the drive elements on a hollow shaft. In this case, too, after all the drive elements have been positioned, all the drive elements are jointly joined on the hollow shaft by simultaneously expanding the hollow shaft in the individual portions associated with the drive elements. The drive elements are positioned with respect to their axial and angular positions by electromagnetic forces. Given the magnetic properties of the drive elements and of the hollow shaft, however, the accuracy of this method of positioning raises concerns. Moreover, the device in which the hollow shaft is held has a horizontal axis which is very difficult to automate.
U.S. Pat. No. 5,054,182 discloses methods and devices for joining a shaft of the above-mentioned type, wherein all the drive elements are first slid on to a hollow shaft and wherein the hollow shaft is then inserted into an overall device which comprises a divisible die for each individual drive element. Each divisible die holds the respective element in a predetermined axial and angular position relative to the hollow shaft and the remaining drive elements, respectively. Various embodiments disclose part axes in a horizontal position and part axes in a vertical position. These devices are very difficult to automate. In addition, they are totally unsuitable for shafts with different designs because each joint type requires its own set of die inserts. The overall device has to be newly set up for the axial positions of the individual divisible dies.
The above-mentioned methods have common disadvantages in that, because of the large number of operating portions of the probe, the number of possible faults which might occur is increased, and it is not easy to immediately identity the source of the fault. If the hydraulic pressure curve is indicating any malfunction while the probe is being operated, the entire assembled shaft has to be regarded as a reject.
If different hydraulic pressures have to be applied to different individual portions of the hollow shaft, for example for a spur gear flange on the one hand and for cams on the other hand, this can only be achieved by means of a highly complicated probe design.
Within a relatively short time, the unavoidable wear of the annular seals at the probe, which seals delimit the operational portions in pairs, leads to the need to replace the annular probe seals. This is a complicated operation.